The role of hemin in the control of globin and other protein synthesis is being explored by the isolation and purification of the inhibitor protein which is active in the absence of hemin, and of the initiation factor involved in the binding of the initiator tRNA to the 40S subunit. By determining the interaction of these purified proteins and the role of hemin in this interaction we should be able to define the regulatory function of heme in protein synthesis. The generality of this effect will be studied by examining the effects of heme deficiency and of added hemin in the synthesis of proteins to nonerythroid tissues. A systematic examination of the protein phospholipid, glycoprotein, and glycolipid constituents of mammalian erythroid cell membranes is being pursued. The eventual objective is the characterization of the changes which occur in normal erythroid cell development and in human hematologic disorders.